Oil spills and pollution contaminate surfaces and waters. A prime example was the Exxon Valdez shipwreck which released large quantities of oil into pristine Alaskan waters and caused very serious environmental damage. Similar polluting events occur frequently around the world. There are products and systems sold that can absorb or collect such oily wastes. However, inexpensive natural products are likely to be highly preferable, useful, and beneficial for such purposes. Materials with high levels of humic acids are known to absorb apolar organic compounds, probably by both partitioning of the organic compounds into hydrophobic regions of the humic substances and by hole filling (Xing, B., “Nonlinearity and Competitive Sorption of Hydrophobic Organic Compounds in Humic Substances,” In Humic Substances Structure Properties and Uses, edited by G. Davies, E. A. Ghabbour and K. A. Khairy. Cambridge, UK: The Royal Society of Chemistry (1998)). However, the use of such materials as remediants for spills and the like has not been previously proposed.
There are large amounts of plant materials that are produced, as by-products of economic activities, which are themselves waste materials. Some of these materials are derived by animal processing; for example, ruminant animals can digest some lignocellulosic plant materials to a fairly high extent, ranging from about 82% for timothy grass to only 6% for ground lodgepole pine wood. The complex lignin fraction is basically unavailable to ruminants; the limit of digestion for each material is the “digestion ceiling,” so that the level of lignin determines this ceiling. Some materials, such as bark from trees removed in lumber operations, waste wood removed and shredded in land-clearing operations, and the indigestable fractions of animal feeds are all produced in large quantities. These contain high levels of lignins—i.e. humic substances. In the latter case, many large confined animal operations collect manures as slurries and separate the liquid phase from solids. The liquid suspensions may be processed via anaerobic fermentation and spread on land. The solid materials may be collected, composted, and sold as low value horticultural supplements. Similarly, barks or woods may (a) be composted to a fine dark powder or (b) processed to make mulches. As with the composts produced from manure solids, the composts or mulches from waste wood products usually are sold to homeowners and landscapers as soil amendments or plant mulches. The mulch products may be divided further into aged mulches, where the material is piled and kept for several months, or raw mulches which are sold directly. The aged mulches have advantages in that salts, sugars, and soluble phenolic compounds largely have been removed. Without such processing, the wood products have potential to be phytotoxic. In general, barks, shredded waste woods and dewatered manures are wastes that are costly to dispose of, having few advantageous uses. The products produced by aging or composting yield products whose sale permits recovery of only a portion of the costs associated with their production.
Other composts may be produced from diverse materials, including food plant wastes, manures, mixed or monolithic organic waste streams from cities or towns, or, less commonly, from animal or fish wastes or flesh. Composts also frequently are formed from sewage biosolids, where anaerobic digestion may be followed by composting of the separated solids, as is the case with animal composts. Typically, composting is an aerobic process and is typified by rapid microbial growth with turning or other aerating systems within a prescribed moisture level. Thermal composting consists of three phases. In the first phase, temperatures in the compost materials begin to rise due to microbial degradation. During the second phase, due to degradation of more resistant compounds like cellulose, temperatures reach 40 to 65° C., a temperature where most microorganisms die. The composts must be turned, aerated, or otherwise handled in a second phase to achieve complete exposure to the high temperatures, ensuring microbial breakdown of available substrates and a homogenous product. Once temperatures decline due to depletion of substrates, the third, or curing phase begins, where microbial recolonization occurs and the percentage of humic substances increase. Typical composts are dark and consist largely of lignins, humic substances, and microbial biomass (Hoitink et al., “Status of Compost-amended Potting Mixes Naturally Suppressive to Soilborne Diseases of Floricultural Crops,” Plant Dis 75(9):869-873 (1991)). This differs significantly from the aging process that may be used with wood bark materials. In the aging process, there is no turning or aeration of the materials, and, consequently, the more resistant portions of the bark or wood retain their integrity to give a fibrous, particulate material.
In a different process, known as vemicycling, temperatures are kept at a lower level (less than 55° C.) and earthworm activity is fostered by inoculation. A typical process for vermicycle composting is disclosed in U.S. Pat. No. 5,082,486. Such products may have properties that differ from those produced by thermal composting. In some cases, thermal composting is followed by vermicycling.
The substrate and process used to produce the composted materials affect the properties of the final products. However, composted or aged products can be produced that are reasonably similar from batch to batch, particularly if the compost substrate is kept constant. However, there are significant variations between composts prepared by different methods and original substrates. Therefore, production and use of any of these materials requires characterization/quality control steps in order to obtain a consistent product.
These materials are produced in large quantities, with some, especially manure solids and wood or bark waste materials, having few uses.
U.S. Pat. No. 3,771,653 teaches the use of composted plant materials that float on water for absorbing and removing oils from water surfaces. A sinking compost formulation is described that is prepared by adding one part compost to two parts sand that is adhered to the compost by the inclusion of 1% crude oil. The sand:compost mix is sufficiently dense that when added to oils on water, the compost sinks. However, sinking composts are only taught to be useful if prepared from materials that float.
U.S. Pat. No. 5,135,578 teaches the use of pellets (in accordance with U.S. Pat. No. 4,788,936) formed from poplar or aspen wood and bark treated with steam. These pellets were effective in absorbing oils from water or sand at a ratio of one part of oil by weight to one part of pellets. A fine net is spread over the oil slick in water before the compost was air dropped. The netted produce is ultimately hauled away.
U.S. Pat. No. 5,795,842 teaches an oil absorbing article with an outer layer of oil-absorbent felt surrounding pine bark. The oil absorbing materials of Japanese Patent Application Serial Nos. 2002180447 and 20002233182 are similar, except that the outer material differs. Likewise, Japanese Patent Application Serial No. 20002233182 describes the use of large pieces of bark contained in a net with an internal rope.
Japanese Patent Application Serial No. 6134299 discloses the production of wood bark treated with a hydrophobic and aseptic agent for the absorption of oil.
U.S. Pat. No. 5,044,324 teaches that grists of assorted wood types are combined and admixed, dried, moisturized, pelletized, and ground to form ‘crumbles.’ These manufactured products can then be used to absorb animal excretions and petroleum.
U.S. Patent Publication No. 20030085174 relates to the use of cellulose-based materials packed into a column for decontamination of various biological fluids. However, the inventors of the present application have found that cellulose-containing materials are not effective, and, in fact, materials with high levels of cellulose work quite poorly.
In commercial practice today, there are several materials that are used in large quantities for removal of oil. Those intended for use on solid surfaces, such as filling station and garage floors, tend to be cheap and are dominated by loose clay-based products, composed entirely or primarily of montmorillonite, bentonite, or similar dried and granulated clays. These materials are very inexpensive and are similar to “kitty litter” type products. They have relatively high bulk densities and may form slimy layers when wet. They also have low oil-holding capacities.
For oil removal from water, spill kits for oily wastes, and other demanding applications, petroleum-derived products, such as pads formed of melt-blown polypropylene (e.g., the linings of baby diapers), are materials of choice. These materials are robust and have much higher oil holding capacities per unit weight than clays, but they are prepared from petroleum and are, therefore, sensitive to increases in the price of crude oil.
Other materials are used as well but in smaller quantities. One example is peat moss, which is a nonrenewable resource. However, its cost is also increasing as peat becomes a more scarce resource.
The present invention is directed to overcoming the deficiencies in the art.